Some data storage systems use redundant storage techniques for protecting data stored in memory against failures. A well-established family of redundant storage techniques is known as Redundant Array of Inexpensive Disks (RAID). For example, U.S. Patent Application Publication 2010/0017650, whose disclosure is incorporated herein by reference, describes a non-volatile memory data storage system, which includes a host interface for communicating with an external host, and a main storage including a first plurality of Flash memory devices. Each memory device includes a second plurality of memory blocks. A third plurality of first stage controllers are coupled to the first plurality of Flash memory devices. A second stage controller is coupled to the host interface and the third plurality of first stage controller through an internal interface. The second stage controller is configured to perform RAID operation for data recovery according to at least one parity.
As another example, U.S. Patent Application Publication 2009/0204872, whose disclosure is incorporated herein by reference, describes a Flash module having raw-NAND Flash memory chips accessed over a Physical-Block Address (PBA) bus by a controller. The controller converts logical block addresses to physical block addresses. In some embodiments, data can be arranged to provide redundant storage, which is similar to a RAID system, in order to improve system reliability.